Glass moulded parts and plastics moulded parts become electrostatically charged by friction or application of charges, for example electron beams in TV picture tubes. As a result of these charges the moulded parts rapidly become covered with dust due to attraction of dust, which is undesirable in practice. There is therefore the need to protect these moulded parts against electrostatic charging. This protection can be achieved for example by coating the moulded parts with an antistatic coating. Following the definition given in ISO 2878, antistatic materials are understood to be those having surface resistances of between 50 k.OMEGA./{character pullout} and 100 M.OMEGA./{character pullout}. Conducting materials are defined as those having surface resistances of &lt;50 k.OMEGA./{character pullout}.
With sufficiently conducting materials, in addition to the antistatic effect a screening effect against electromagnetic radiation, as is emitted for example from cathode ray tubes, is also achieved. For an effective radiation screening the surface resistance must be less than 3 k.OMEGA./{character pullout}.
For practical use these coatings must also have a sufficient mechanical strength and adhesion. Especially in the case of glass as carrier, the layers must be sufficiently scratch-resistant in order to avoid damage to the coating when cleaning the coated surfaces and thus loss of the antistatic and/or conducting effect.
Electrically conducting polymers, for example polythiopenes, for producing antistatic and/or conducting coatings are known from the literature Examples thereof may be found in EP-A 440 957 and DE-OS 42 11 459.
The use of these polythiophene salts for giving glass an antistatic finish is described in DE-OS 42 29 192. It has been found however that these coatings are not sufficiently scratch-resistant in practice for some applications.
Scratch-resistant coatings based on hydrolysed siloxanes are known from EP-A 17 187. These however are not compatible with preparations of polythiophene salts.
Poly-3,4-ethylenedioxythiophene-containing coatings on image screens are described in WO 96/05606. In order to improve the scratch resistance of the coatings and obtain anti-reflecting properties, layers of SiO.sub.2 and/or TiO.sub.2 obtained for example from metal alkoxides are applied thereto via the sol-gel process.
A disadvantage is that already with layer thicknesses that are only slightly more than 100 nm, the transmission falls below 60%. The layer must therefore have exactly the same thickness over the whole surface. The reproducible application of such thin coatings is however technically difficult.
A further disadvantage of this process is that conducting coatings having the required scratch resistance can only be obtained if the conducting layer is provided with at least one scratch-resistant covering layer. To obtain suitable coatings having anti-reflecting properties it is necessary to apply up to four different layers in succession. This is technically extremely complicated. Also, with each additional layer there is an increasing danger that the overall laminar composite will exhibit a defect.
The object of the present invention was accordingly to provide mixtures which, when applied to suitable substrates, produce after removal of the solvents firmly adhering, conducting coatings having improved scratch resistance and transmission of visible light.
It has now been found that the aforementioned requirements can be fulfilled if mixtures of conducting organic polymers with reaction products of polyfunctional organosilanes and optionally further components such as metal alkoxides, metal oxides or metal oxide-hydroxides are used.